Eyestrain (commonly called asthenopia) / by Ernest Clarke.

  • Ernest Clarke
Date:
1892
Catalogue details

Licence: Public Domain Mark

Credit: Eyestrain (commonly called asthenopia) / by Ernest Clarke. Source: Wellcome Collection.

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    to have seen cases of insufficiency of the oblique muscles. This is the result of the superior oblique of either eye being too strong for its inferior, or vice versd. The parallelism of the vertical meridians of the corneae is maintained by the equilibrium of these muscles ; hence, if one muscle is weaker, excessive work must be put upon it in order to preserve the parallelism, and Savage says that a train of nervous symptoms are thus brought on, for which at present there seems no hope of cure. The presence of these insufficiencies is revealed by the Maddox glass rod test (see Oph. Rev., vol. ix., p. 129, A New Test for Heterophoria ). V. CAUSES OF MUSCULAR ASTHENOPIA.—Mus- cular asthenopia is much less common than ciliary asthen- opia. I have notes of 94 cases of the former as against 323 of the latter. V. Graefe said that out of 100 eye-patients presenting themselves to him, about 10 suffered from asthenopia, and of these 10, one was a case of muscular asthenopia.-^ Heterophoria, the result of muscular insufficiency, in most cases lies at the bottom of the causes of muscular asthenopia. Table of Causes. In Emmetropia, due to :— i. Abuse in the healthy (excessive orprolonged convergence). ii. Nervo-muscular debility : {a) Neurasthenia. ib) General debility. iii. Congenital defect. In Ametropta, in :— i. Hyperopia (high). ii. Myopia. iii. Astigmatism. iv. Anisometropia.
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